Bienzymatic-based electrochemical DNA biosensors: a way to lower the detection limit of hybridization assays.

The use of the alkaline phosphatase (AP) as an enzyme label and the amplification of its analytical response with a diaphorase (DI) secondary enzyme were investigated in an electrochemical hybridization assay involving arrays of carbon screen-printed DNA biosensors for the sensitive quantification of an amplified 406-base pair human cytomegalovirus DNA sequence (HCMV DNA). For this purpose, PCR-amplified biotinylated HCMV DNA targets were simultaneously bound to a monolayer of neutravidin irreversibly adsorbed on the surface of the electrodes and hybridized to complementary digoxigenin-labeled detection probes. The amount of hybrids immobilized on the electrode surface was labeled with an anti-digoxigenin AP conjugate and quantified electrochemically by measuring the activity of the AP label through the hydrolysis of the electroinactive p-aminophenylphosphate (PAPP) substrate into the p-aminophenol (PAP) product.

Evaluation of the analytical performances of avidin-modified carbon sensors based on a mediated horseradish peroxidase enzyme label and their application to the amperometric detection of nucleic acids.

In this study, neutravidin-coated screen-printed carbon sensors were fully characterized and further used for the amperometric detection of specific DNA sequences of human cytomegalovirus (HCMV DNA). For this purpose, we took advantage of an earlier established relationship between the amount of HRP affinity immobilized on the surface of the electrode and the steady-state current recorded in the presence of H(2)O(2) as substrate and the single electron donor [Os(III)(bpy)(2)pyCl](2+) as cosubstrate. After incubating a saturating concentration of biotinylated horseradish peroxidase (Bio-HRP) onto the neutravidin-modified sensors, a surface concentration of active HRP of 3.

Subfemtomolar electrochemical detection of target DNA by catalytic enlargement of the hybridized gold nanoparticle labels.

After showing the failure of conventional gold-enhancement procedures to amplify the gold nanoparticle-based electrochemical transduction of DNA hybridization in polystyrene microwells, a new efficient protocol was developed and evaluated for the sensitive quantification of a 35 base-pair human cytomegalovirus nucleic acid target (tDNA). In this assay, the hybridization of the target adsorbed on the bottom of microwells with an oligonucleotide-modified Au nanoparticle detection probe (pDNA-Au) was monitored by the anodic stripping detection of the chemically oxidized gold label at a screen-printed microband electrode (SPMBE). Thanks to the combination of the sensitive Au(III) determination at a SPMBE with the large amount of Au(III) released from each pDNA-Au, picomolar detection limits of tDNA can be achieved.

Influence of pendant arms bearing ligating groups on the structure of bismuth porphyrins: implications for labeling immunoglobulins used in medical applications.

The synthesis of two picket bismuth(III) porphyrins is reported, and their crystal structures are compared. The influence of the nature of the pickets, as well as their number, is discussed in terms of stability, kinetics of metalation, structure, and distortion of the porphyrin. Unexpectedly, the results indicate that the coordination sphere of bismuth is not affected by different types of distortion nor is the stability of the complex.

Covalent immobilization of oligonucleotides on p-aminophenyl-modified carbon screen-printed electrodes for viral DNA sensing.

DNA-sensing platforms were prepared by covalently attaching oligonucleotide capture probes onto p-aminophenyl-functionalized carbon surfaces and applied to the determination of an amplified herpes virus DNA sequence in an electrochemical hybridization assay.

[Contribution of simultaneous multiple immunoassays to biology].

During the last years, research in the area of immunoanalysis has been oriented towards the marketing of more reliable, faster and low cost kits. In this field, simultaneous multiple immunoanalysis that offer long-time ignored original and specific advantages, has undergone tremendous improvements triggered by striking technological innovations and the advent of lanthanide chelate based markers. Simultaneous multiple immunoassays have turned from semi-quantitative methods restricted to pharmacology to quantitative methods for medical biology.

Gold nanoparticle-based quantitative electrochemical detection of amplified human cytomegalovirus DNA using disposable microband electrodes.

An electrochemical DNA detection method has been developed for the sensitive quantification of an amplified 406-base pair human cytomegalovirus DNA sequence (HCMV DNA). The assay relies on (i) the hybridization of the single-stranded target HCMV DNA with an oligonucleotide-modified Au nanoparticle probe, (ii) followed by the release of the gold metal atoms anchored on the hybrids by oxidative metal dissolution, and (iii) the indirect determination of the solubilized AuIII ions by anodic stripping voltammetry at a sandwich-type screen-printed microband electrode (SPMBE). Due to the enhancement of the AuIII mass transfer by nonlinear diffusion during the electrodeposition time, the SPMBE allows the sensitive determination of AuIII in a small volume of quiescent solution.

[Evaluation of the quality drug prescription for patients to be discharged from a university teaching hospital: statutory aspects].

The aim of this work was to assess the quality of written drug prescriptions for patients to be discharged from our hospital. The pharmacological pertinence was not evaluated. Each statutory mention was noted according to a binary system: 1=mention present, 0=mention not present.

Hybridization assay at a disposable electrochemical biosensor for the attomole detection of amplified human cytomegalovirus DNA.

A disposable electrochemical biosensor for the detection of DNA sequences related to the human cytomegalovirus (HCMV) is described. The sensor relies on the adsorption of an amplified human cytomegalovirus DNA strand onto the sensing surface of a screen-printed carbon electrode, and to its hybridization to a complementary single-stranded biotinylated DNA probe. The extent of hybrids formed was determined with streptavidin conjugated to horseradish peroxidase.

Carbonyl metallo immuno assay: a new application for Fourier transform infrared spectroscopy.

We describe here the development of a new, non-isotopic immunological assay termed CMIA (carbonyl metallo immunoassay) that uses metal carbonyl complexes as tracers and Fourier transform infrared spectroscopy (FT-IR) as the detection method. This assay is based on the particular spectral features of these complexes, which show very strong absorption bands in the 1,800-2,200 cm(-1) spectral range where proteins and organic molecules do not absorb. In Section 1, the optimisation of the quantitative detection of these tracers is detailed.

Quantitative analysis of mixtures of metal-carbonyl complexes by Fourier-transform infrared spectroscopy: application to the simultaneous double immunoassay of antiepileptic drugs by the nonisotopic carbonyl metalloimmunoassay method.

The feasibility of a double immunoassay of haptens by the nonisotopic carbonyl metalloimmunoassay (CMIA) method is demonstrated. Three different pairings of antiepileptic medications from the groups carbamazepine, diphenylhydantoin, and phenobarbital (for each of which a mono-CMIA is already available) were assayed by double CMIA. The assay method employs as tracers metal-carbonyl complexes that give very strong signals in the range of 1850-2200 cm-1 in the infrared spectrum, permitting quantitative analysis by Fourier-transform infrared spectroscopy.

[Study of an anti-serum against phenytoin with two organometallic tracers].

In order to develop a new immunoassay procedure based on the use of organometallic labels, an antiserum is raised against antiepileptic drug: diphenyl-hydantoin (phenytoin). Immunization was performed in rabbits with phenytoin coupled to bovine-serum albumin. The evaluation of the specificity and the affinity constants of the antiserum is studied by radioimmunoassay against different antiepileptic drugs and metallotracers (phenytoin labelled with organometallic fragments derived respectively from cobaltocene and ferrocene).

Production of specific antibodies and development of a non-isotopic immunoassay for carbamazepine by the carbonyl metallo-immunoassay (CMIA) method.

As part of our ongoing work to extend the range of applications of the non-isotopic carbonyl metalloimmunoassay (CMIA), previously developed in our laboratory, we describe here the first CMIA study of carbamazepine. The CMIA method uses a metal carbonyl complex as a non-isotopic tracer, and in this case we chose to employ the dicobalt hexacarbonyl moiety (Co2(CO)6) attached to an alkyne. Two organometallic tracers, 3 and 7, were synthesized, differentiated by the nature and length of the spacer arm of the Co2(CO)6 moiety.

Application of the non-radioisotopic carbonyl metalloimmunoassay (CMIA) to diphenylhydantoin.

As part of our ongoing work to develop the new non-isotopic assay method carbonyl metalloimmunoassay (CMIA), whose efficacy has already been proven in the laboratory for phenobarbital and cortisol, we here present the steps involved in establishing CMIA of 5,5 diphenylhydantoin (DPH), one of the most commonly used antiepileptic medications. First, anti-DPH antibodies were obtained by injection of the immunogen DPH-3-valerate-BSA into rabbits. The titer value and specificity of these antibodies were examined by RIA using [14C]-DPH as tracer, and an antibody batch selected for its high titer value and good specificity for metabolites of DPH and other antiepileptic drugs.

Atomic absorption spectrometric detection of biotin-cymantrene as a metallo-tracer for the avidin-biotin system.

Biotin-cyclopentadienylmanganese tricarbonyl (biotin-cymantrene; biotin-Cy) is proposed as a universal metallo-tracer for immunoassays. Associated with the possibility of detecting this type of label (organometallic moieties) along with different analytical procedures, this reagent appears to be a universal system with the advantages of being inexpensive, stable and directly detected (no substrate is required). The optimum conditions for detecting the organometallic label biotin-Cy with a Zeeman atomic absorption spectrometer and the affinity of biotin-Cy for the streptavidin ligand immobilized on the walls of microtitre plates, wells or tubes are described.

Use of Fourier transform infrared spectroscopy for the simultaneous quantitative detection of metal carbonyl tracers suitable for multilabel immunoassays.

We describe here a new approach for multilabel immunoassays. The starting point of this approach is a new nonradioisotopic immunoassay (carbonyl metallo immunoassay) based on the use of metal carbonyl complexes as tracers and Fourier transform infrared (FT-ir) spectroscopy as the detection method. We show here that the judicious choice of the organometallic tracers associated with multicomponent analysis of FT-ir spectroscopic data provides the simultaneous rapid and reliable quantitation of pmol of the organometallic tracers.

Carbonylmetalloimmunoassay (CMIA) a new type of non-radioisotopic immunoassay. Principles and application to phenobarbital assay.

A new non-radioisotopic immunoassay procedure, which we have termed carbonylmetalloimmunoassay (CMIA), is described. The tracers used in this approach are organometallic carbonyl complexes that can be detected at femtomole levels (300-700 fmol) by Fourier transform infrared (FT-IR) spectroscopy. The validity of the technique has been tested in a phenobarbital assay using as the marker a cyclopentadienylmanganese (I) tricarbonyl (cymantrene) moiety, ethyl acetate extraction to separate the free and bound organometallic fractions, and FT-IR spectroscopy to detect the CO stretching modes of the organometallic label.

Potentiality of an organometallic labelled streptavidin--biotin system in metalloimmunoassay.

Biotin labelled with a cymantrene moiety (cyclopentadienyl manganese tricarbonyl complex) is described for the first time. Because this metallo-biotin retains full recognition for the specific glycoprotein avidin (or streptavidin), the labelled streptavidin-biotin system is proposed for use in a solid-phase competition-type metalloimmunoassay in which bovine serum albumin (BSA) is used as a model of applications. Atomic absorption spectrometry is utilized for the detection of the cymantrene-labelled biotin.

[An antiserum directed against phenobarbital with an organometallic tracer: production and characterization].

In order to develop a new immunoassay procedure based on the use of organometallic labels, antisera are raising against sedative-hypnotic drug: phenobarbital. Immunization was performed in rabbits with parasuccinylamidophenobarbital coupled to bovine-serum-albumin. The evaluation of the specificity and the affinity constants of antisera are studied against different hypnotic or antiepileptic drugs and the metallotracer (phenobarbital labelled with an organometallic fragment derived from cymantrene).

A new powerful association for immunoassay: organometallic label conjugated to solvent separation method.

The convenient use of solvents as a method to separate free (F) and bound (B) fractions in drug immunoassays which utilize organometallic moieties as labels, has been developed. Two types of drugs labelled with an organometallic complex and denominated metallohaptens (or metallotracers) are studied as model assays: desipramine (tricyclic antidepressant) and phenobarbital (antiepileptic agent). Different organic solvents have potentialities to extract these metallohaptens.

Infrared immunoassay.

An immunoassay method based on the labelling of an antigen with a transition-metal carbonyl organometallic marker and detection of the label by Fourier transform infrared (FT-IR) spectroscopy is described. The viability of this novel non-isotopic approach, termed infrared immunoassay (IRIA), has been evaluated in the quantitative determination of the tricyclic antidepressant nortriptyline.

Metalloimmunoassay of tricyclic antidepressant drugs: production and characterization of antiserum.

Metalloimmunoassay is a new immunoassay using an organometallic complex as the label. For the development of this assay, antibodies were produced in rabbits immunized with N-succinyldesipramine-bovine serum albumin conjugate. Antisera thus obtained were shown to be specific for the tricyclic antidepressant group of drugs and are tested as regard as desipramine or nortriptyline labelled by an organometallic moiety (designated metallohaptens).